A DC/DC converter is a circuit that converts a direct current voltage input from a direct current voltage source to a different direct current voltage. “DC” is an abbreviation for Direct Current. The DC/DC converter is roughly divided into three types: a step-up DC/DC converter, a step-down DC/DC converter, and a step-up/step-down DC/DC converter. The step-up DC/DC converter is a circuit that converts an input direct current voltage to a larger direct current voltage. The step-down DC/DC converter is a circuit that converts an input direct current voltage to a smaller direct current voltage. The step-up/step-down DC/DC converter is a circuit that is capable of both conversion to a direct current voltage larger than an input direct current voltage and conversion to a direct current voltage smaller than an input direct current voltage.
Typically, the step-up DC/DC converter boosts an input direct current voltage using a turns ratio of a transformer. In the step-up DC/DC converter with a large ratio of output to input, the turns ratio of the transformer is large, resulting in poor conversion efficiency.
Non-Patent Literature 1 discloses a DC/DC converter configured by connecting a plurality of power conversion circuits in series as a power conversion apparatus for an electric propulsion device such as an ion engine. In this DC/DC converter, in addition to a series-resonant power conversion circuit with a fixed output voltage to achieve high conversion efficiency, a different power conversion circuit with a variable output voltage is provided. The overall output voltage is adjusted by adjusting the output voltage of this different power conversion circuit.
Non-Patent Literature 2 discloses a DC/DC converter configured by connecting a plurality of power conversion circuits in parallel as a power conversion apparatus for an electric propulsion device. In this DC/DC converter, one of the power conversion circuits operates as a master and the rest of the power conversion circuits operate as slaves. The overall output voltage is adjusted by adjusting the output voltage of the master while the output voltages of the slaves are fixed.